CLN: Remove unnecessary rolling subclass (#36721)

* Remove unnecessary subclass

* Rename _Window -> BaseWindow

* Add Rolling._constructor property

* Black

Co-authored-by: Matt Roeschke <[email protected]>

Author: mroeschke

pandas/core/window/ewm.py

@@ -15,7 +15,7 @@
 
 import pandas.core.common as common
 from pandas.core.window.common import _doc_template, _shared_docs, zsqrt
-from pandas.core.window.rolling import RollingMixin, flex_binary_moment
+from pandas.core.window.rolling import BaseWindow, flex_binary_moment
 
 _bias_template = """
         Parameters
@@ -60,7 +60,7 @@ def get_center_of_mass(
     return float(comass)
 
 
-class ExponentialMovingWindow(RollingMixin):
+class ExponentialMovingWindow(BaseWindow):
     r"""
     Provide exponential weighted (EW) functions.
 

pandas/core/window/rolling.py

@@ -147,7 +147,9 @@ def func(arg, window, min_periods=None):
     return func
 
 
-class _Window(ShallowMixin, SelectionMixin):
+class BaseWindow(ShallowMixin, SelectionMixin):
+    """Provides utilities for performing windowing operations."""
+
     _attributes: List[str] = [
         "window",
         "min_periods",
@@ -184,10 +186,6 @@ def __init__(
         self.axis = obj._get_axis_number(axis) if axis is not None else None
         self.validate()
 
-    @property
-    def _constructor(self):
-        return Window
-
     @property
     def is_datetimelike(self) -> Optional[bool]:
         return None
@@ -862,7 +860,7 @@ def aggregate(self, func, *args, **kwargs):
     )
 
 
-class Window(_Window):
+class Window(BaseWindow):
     """
     Provide rolling window calculations.
 
@@ -1040,6 +1038,10 @@ class Window(_Window):
     2013-01-01 09:00:06  4.0
     """
 
+    @property
+    def _constructor(self):
+        return Window
+
     def validate(self):
         super().validate()
 
@@ -1220,13 +1222,7 @@ def std(self, ddof=1, *args, **kwargs):
         return zsqrt(self.var(ddof=ddof, name="std", **kwargs))
 
 
-class RollingMixin(_Window):
-    @property
-    def _constructor(self):
-        return Rolling
-
-
-class RollingAndExpandingMixin(RollingMixin):
+class RollingAndExpandingMixin(BaseWindow):
 
     _shared_docs["count"] = dedent(
         r"""
@@ -1939,6 +1935,10 @@ def _on(self) -> Index:
                 "must be a column (of DataFrame), an Index or None"
             )
 
+    @property
+    def _constructor(self):
+        return Rolling
+
     def validate(self):
         super().validate()